Rotary impact hammer



Filed April 1964 INVENTQ Ambrose W Drew ATTORNEY.

r 3,268,014 [Ce Patented August 23, 1966 Filed Apr. 17, 1964, Ser. No.360,719 3 Claims. (Cl. 17397) This application is a continuation-in-partof application, Serial No. 251,180, filed January 14, 1963, now Patent3,149,681.

This invention relates generally to tools and is more particularlyconcerned with a rotary hammer device for simultaneously rotating andaxially impacting a tool bit and other member.

Conducive to a better understanding of the invention, it may be well topoint out that tools of this type have a common defect in that they aresubject to excessive heating, due to friction generated between theimpacting elements which comprise a rotating anvil portion against whicha non-rotating hammer is repeatedly driven. Since the anvil and itsshaft are ordinarily operated at speeds of 1800 r.p.m., it will beevident that even during the short period of impact there is asubstantial frictional drag between the stationary and rotating parts.

To reduce the heating effect, various schemes of lubrication, coolingair circulation, and heat dissipating fins have been used.

The primary object of this invention, therefore, is to provide a rotaryimpact hammer whose anvil and hammer elements rotate together andimpact, without relative rotation, in friction free engagement.

Another object is to provide a device of the type stated whose toolholding element is free to move axially of its center of rotation underimpact.

A further object is to provide a rotary hammer mechanism for rotating adrill bit, or the like, and simultaneously applying frictionless axialimpacts thereto, which device is simple in construction, fullyadjustable as to the force of the delivered impact, heat free inoperation, and relatively inexpensive to manufacture.

With the foregoing and other objects in view which will appear as thedescription proceeds, the invention resides in the combination andarrangement of parts and in the details of construction hereinafterdescribed and claimed, it being the intention to cover all changes andmodifications of the example of the invention herein chosen for purposesof the disclosure, which do not constitute departures from the spiritand scope of the invention.

The invention is illustrated in the accompanying drawing, wherein:

FIGURE 1 is a longitudinal sectional view of the rotary hammer device.

FIGURE 2 is a longitudinal sectional view of an alternate form of thedevice.

FIGURE 3 is a horizontal section on line 33 of FIGURE 2.

FIGURE 4 is a side elevation of the hammer portion shown in FIGURES 2and 3.

By referring to the drawing, and FIGURE 1 in particular, it will be seenthat the rotary impact hammer that is the subject of this invention isadapted to be mounted on a conventional portable electric drill casehaving a shoulder and a motor drive shaft 11.

An elongated, hollow housing 12 is mounted on the shoulder 10 through acollar 13, which is fitted over the shoulder 10 and clamped thereon bymeans of a bolt 14.

The housing 12 is threaded at its forward end 15 and a cam cap 16,having internal threads, is mounted on the housing threads and rotatablethereon. The cap 16 has a centered hole 17 therethrough.

A cam ring 18 is mounted inside the cap 16 by means of screws 19. Thecam ring 18 also has a central bore 20 surrounded by a series of sharplyinclined and spaced cam teeth 21 rising to an abruptly vertical end face22. A rotating axially movable spindle 23 is mounted on the threaded endof the motor drive shaft 11, through a coupling sleeve 24 so as to forma continuation thereof. A bearing 25 serves as a journal supporting thesleeve 24 in the housing 12. The spindle 23 extends through the housing12 and beyond the end cap 16. The cam ring 18 has a shouldered secondarybore which holds a bearing unit 26 which supports the spindle 23 in thehousing 12 adjacent the end cap 16. The coupling 24 has a bore 27therethrough which is threaded at one end to engage the threaded end ofthe motor drive shaft 11 as heretofore described, and the other end ofthe sleeve 24 has a diametrical slot 28 cut thereacross.

The free end of the spindle 23 is threaded as at 29 to receive a toolholding device, such as a drill chuck, not illustrated.

A secondary coupling sleeve 30, having a diametrically disposedupstanding key 31 which mates with slot 28 of the coupling sleeve 24, ismounted on the spindle 23, which extends therethrough in a free slidingfit.

The secondary coupling sleeve 30 has a pair of aligned longitudinallyextending slots 32 cut through the walls thereof, which are engaged by apin 33 mounted through the spindle 23 and which acts to lock the sleeve30 and spindle 23 against relative rotation but leaves the spindle 23free to reciprocate axially in the sleeve within the length of the slots32.

It will be seen that there is no direct connection between the spindle23 and the motor drive shaft 11, so that the spindle 23 is free toreciprocate in the two coupling sleeves 24 and 30, toward or away fromthe drive shaft 11.

The spindle 23 has an anvil 34 thereon adjacent the end face 22 of thecams 21 and the anvil 34 may be either formed integral with the spindle23 or may be a separate piece, immovably mounted thereon. The anvil 34is located within the counter bore 20 of the cam ring 18.

The cam ring 18 has four cam track teeth 21 thereon.

A hammer 35 is slidably mounted, through a central bore 36, on thespindle 23, inwardly of the cam ring 18. The hammer has four camfollower balls 37 embedded therein which operate co-operatively with theteeth 21 of the cam ring 18. An annular head is formed on the hammer 35faced toward and aligned with the anvil 34. An elongated slot 38 cutthrough the opposed walls of the hammer 35 is engaged by a pin 39mounted through the spindle 23. The pin 39 acts to lock the hammer andspindle against relative rotation, but leaves the hammer 35 free toreciprocate longitudinally of the spindle 23, the length of the slots38.

The hammer 35 is normally biased toward the anvil 34 and in contact withthe cam teeth 21 'by a spring 40 anchored at one end in a groove 41 inthe coupling sleeve 30 and seated at its other end in a second groove 42in the hammer 35.

It will now be evident that the anvil 34 and the hammer 35 rotate withthe spindle 23 and at the same speed as the spindle. As a result, whenthe hammer 35 is impacted against the anvil by the co-operative actionof the camming components together with the biasing action of the spring40, there is no wiping or sliding action between the anvil and hammer tocreate friction. Therefore, the device will remain'cool even afterprolonged operation.

Since the spindle 23 is slidably mounted through the coupling sleeve 30,at the moment of impact, the spindle 23 and anvil 34 are free to moveaxially away from the hammer 35 to carry the tool retained on thespindle end 29 forward in the direction of the impact blow, therebyproviding a true hammer impact.

It will occur to those skilled in the art that modifications of thestructure just described are sometimes desirable, and one suchmodification incorporating advantages as hereinafter set forth may beseen, as by referring to FIGURES 2, 3, and 4 of the drawings.

In FIGURE 2 of the drawings, a portion of a case 44 of a portableelectric drill may be seen and which case is provided with a threadedshoulder 45 surrounding a drive shaft 46 and spaced with respect theretoby a bearing assembly 47. The alternate form of the rotary hammer deviceis attached directly to the threaded shoulder 45 and comprises anelongated hollow housing 48 threaded at one of its ends for engagementwith the threaded shoulder 45 of the portable electric drill.

The opposite end of the housing 48 is closed with the exception of acentral opening 49. A coupling sleeve 59 has a threaded socket 51 in oneend thereof which is threaded for engagement on the drive shaft 46 ofthe motor, and the other end of the coupling 59 has a bore 52 thereinfor the reception of one end of a spindle 53. A slot 54 is formed in thespindle 53 and a pin 55 is positioned transversely of the sleeve 50 andthrough the slot 54 so that the spindle 53 may move axially relative tothe sleeve 50. A bearing assembly 56 is mounted in the end of thehousing 48 adjacent the opening 49 and journals the spindle 53, and itwill be seen that this construction hglds the spindle in desired axialposition of the housing 4 An anvil 57 is formed on the spindle 53inwardly of the bearing assembly 56 and within the chamber 58 in thehousing 48 as defined by an annular sleeve 59 which is secured inposition by set screws 60'. The annular sleeve 59 has oppositelydisposed openings 61 therein which partially cage the balls 62 forrelative rotation. A hammer 63 having an axial bore 64 therethrough ispositioned on the spindle 53 in spaced relation to the anvil 57 andincludes a striking face 65 which is adapted to be moved in a reciprocalmotion relative to the anvil 57 so as to impart hammer-like blowsthereto when the spindle 53 and the hammer 63 are revolved.

A secondary slot 66 transversely of the hammer 63 engages a pin 67positioned through a spindle 53 so that the hammer 63 may move withinthe limitations of the slot 66. A coil spring 68 is positioned betweenthe hammer 63 and the coupling 50 and normally biases the hammer 63toward the anvil 57. The hammer 63 has a pair of cams 69 formed thereonin oppositely disposed relation with interconnecting camming surfaces 70and the area of the hammer 63- between the earns 69 and the strikingface 65 is of a reduced diameter so that the balls 62 which comprise camfollowers will engage the annular area of the hammer 63 beyond the earns69 and simultaneously engage the cams 69 and the intermediate cammingsurfaces 70.

It will thus be seen that rotation of the spindle 53 by the motor in theportable electric drill will rotate the hammer 63 relative to the balls62 which comprise cam followers and that the hammer 63 will therefore bemoved in a reciprocal hammering action relative to the anvil 57 and thespindle 53 due to the biasing of the coil spring 68.

It will further be seen that the distance of movement may be varied byvarying the height of the cams 69 so that maximum hammer blows areobtained on the anvil 57.

In FIGURE 3 of the drawings, a cross section on line 33 of FIGURE 2illustrates the balls 62 which comprise cam followers in positionadjacent the earns 69, and in FIGURE 4 of the drawings a side elevationof the hammer 63 and a portion of the spindle 53 on which it is mountedmay be seen with the cams 69 and camming surfaces in plan view.

It will occur to those skilled in the art that the particularconstruction disclosed herein is particularly suitable in a torquewrench of the impact type.

It will thus be seen that an improved alternate construction has beendisclosed which provides for a remarkably increased striking distance ofthe hammer with respect to the anvil as compared with the form of theinvention illustrated in FIGURE 1 and heretofore described.

It will thus be seen that the rotary hammer disclosed herein meets theseveral objects of my invention, and having thus described my invention,what I claim is:

1. In combination with a portable electric drill of the type having acase and a drive shaft protruding therefrom, a rotary impact hammer,comprising, an elongated hollow housing mounted on the case at the driveshaft; a spindle journaled in the housing for rotary and limited axialmovement relative to the housing and extending through the forward endthereof, the spindle having tool holding means at its outer end;coupling means on said spindle, within said housing, for connection tothe motor drive shaft; anvil means comprising a shouldered collarpositioued on the spindle intermediate its ends; hammer means slidablymounted on and keyed to the spindle for rotation therewith and movementaxially thereof between a first position, in engagement with the spindleanvil, and a second position, spaced from the anvil; spring meansmounted on the spindle in pressed egagement with the hammer for normallybiasing the hammer to its first position; said spindle anvil beingmovable between a first and second position, the spindle anvil beingclear of the hammer when the spindle anvil is in its first position; andco-operating cam means on said hammer and housing for alternately movingthe hammer between its first and second positions for imparting impactto the spindle anvil along its axis of rotation when the spindle isrotated in the housing and the spindle anvil is moved to its second,retracted position, against the biasing action of the spring, by reasonof inward pressure by the held tool exerted against the spindle and;said co-operating cam means comprising a plurality of circumferentiallyarranged carnming portions on an annular shoulder of the hammer, androtating therewith, and a plurality of e c-operating, circularlyarranged rotatable cam engaging portions on the housing and heldthereby.

2. A rotary impact hammer for use with a portable electric drill havinga case and a drive shaft protruding therfrom comprising an elongatedhollow housing arranged for attachment to said case at one end, aspindle journalled in said housing for rotary and limited axial movementrelative to said housing, detachable coupling means on said spindleengaging said drive shaft, a cylindrical hammer slidably mounted on saidspindle, means on said spindle engaging said hammer arranged to permitreciprocal movement of said hammer on said spindle, an anvil on saidspindle spaced relative to said hammer and positioned for engagement bysaid hammer, spring means on said spindle biasing said hammer towardsaid anvil, circumferentially arranged interconnecting cam means on saidhammer, an apertured sleeve received in said housing, rotatable camfollowers positioned in said apertured sleeve for registry with said cammeans.

3. A rotary impact hammer for use with a portable electric drill havinga case and a driveshaft protruding therefrom and comprising an elongatedhollow housing arranged for attachment to said case at one end, aspindle journalled in said housing for rotary and limited axial movementrelative to said housing, detachable coupling means on said spindleengaging said driveshaft, a cylindrical hammer slidably mounted on saidspindle, means on said spindle engaging said hammer arranged to permitreciprocal movement of said hammer on said spindle, an anvil on saidspindle spaced relative to said hammer and positioned for engagement bysaid hammer, spring 5 6 means .on said spindle biasing said hammertoward said References Cited by the Examiner anvil, circumferentiallyarranged interconnecting cam UNITED STATES PATENTS means on said hammer,an apertured sleeve in said housing, rotatable cam followers positionedin said apertured 2,293,443 8/1942 Mossberg 173 119 sleeve for registrywith said cam means on said hammer, 5 2,492,840 12/1949 Bugg 17395 saidhammer comprising a solid cylindrical member having 3,123,156 3/ 1964Gapstur 1731 19 two different outer diameters forming a larger portionFOREIGN PATENTS and a smaller portion thereof and wherein said cam meanson said hammer are formed on the larger portion ad- 564,001 9/ 1944Great Brltallh jacent the smaller portion, said smaller and larger por-10 I tions of said hammer being telescopically engaged in said MILTONKAUFMAN 1mm y Examiner apertured sleeve and movable axially relativethereto. LAWRENCE P. KESSLER, Examiner.

2. A ROTARY IMPACT HAMMER FOR USE WITH A PORTABLE ELECTRIC DRILL HAVINGA CASE AND A DRIVE SHAFT PROTRUDING THEREFROM COMPRISING AN ELONGATEDHOLLOW HOUSING ARRANGED FOR ATTACHMENT TO SAID CASE AT ONE END, ASPINDLE JOURNALLED IN SAID HOUSING FOR ROTARY AND LIMITED AXIAL MOVEMENTRELATIVE TO SAID HOUSING, DETACHABLE COUPLING MEANS ON SAID SPINDLEENGAGING DRIVE SHAFT, A CYLINDRICAL HAMMER SLIDABLY MOUNTED SAIDSPINDLE, MEANS ON SAID SPINDLE ENGAGING SAID HAMMER ARRANGED TO PERMITRECIPROCAL MOVEMENT OF SAID HAMMER ON SAID SPINDLE, AN ANVIL ON SAIDSPINDLE SPACED RELATIVE TO SAID HAMMER AND POSITIONED FOR ENGAGEMENT BYSAID HAMMER, SPRING MEANS ON SAID SPINDLE BIASING SAID HAMMER TOWARDSAID ANVIL, CIRCUMFERENTIALLY ARRANGED INTERCONNECTING CAM MEANS ON SAIDHAMMER, AN APERTURED SLEEVE RECEIVED IN SAID HOUSING, ROTATABLE CAMFOLLOWERS POSITIONED IN SAID APERTURED SLEEVE FOR REGISTRY WITH SAID CAMMEANS.